Start by filling up your tank. Write down the odometer reading or reset your trip gauge to zero.

The next time you get gas, fill the tank again and record the odometer or trip gauge reading.

Subtract the previous odometer reading from the current odometer reading.

Divide the result by the number of gallons purchased (or use the number of miles traveled on the trip gauge and divide by the number of gallons purchased). One significant decimal place is sufficient.

Example Scenario: Your odometer reads 30,455 when the tank is first filled. The vehicle is driven until the odometer reads 30,723 when you pull into the gas station. It takes 12.7 gallons to fill the tank again.

Subtract the first reading of 30,455 from 30,723 and divide the result by 12.7. (30,723 - 30,455 = 268; and 268/12.7 = 21.1 mpg].

If using the trip gauge, don’t forget to reset it to zero each time you fill up! You can keep a running record of your gas mileage over the life of your vehicle, if you choose.

So, does that number need a little bit of improving? Try some of these tips:

2. Drive sensibly Aggressive driving including speeding, rapid acceleration and excessive braking wastes gas. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town. Sensible driving is also safer for you and others, so you may save more than gas money.

3. Observe the speed limit Gas mileage decreases rapidly at speeds above 60 mph. Each 5 mph you drive over 60 mph is like paying an additional $0.10 per gallon for gas. Observing the speed limit is also safer.

4. Avoid excessive idling An idling engine is getting 0 miles per gallon. Cars with larger engines typically waste more gas when idling than do cars with smaller engines.

5. Use cruise control Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.

6. Keep your engine properly tuned Fixing a car that is noticeably out of tune or has failed an emissions test can improve its gas mileage by an average of 4.1 percent, though results vary based on the kind of repair and how well it is done. If your car has a faulty oxygen sensor, your gas mileage may improve as much as 40 percent.

7. Check and replace air filters regularly Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent. Your car's air filter keeps impurities from damaging the inside of your engine. Not only will replacing a dirty air filter save gas, it will protect your engine.

8. Keep tires properly inflated You can improve your gas mileage by about 3.3 percent by keeping your tires inflated to the proper pressure. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Properly inflated tires are safer and last longer.

9. Use the recommended grade of motor oil You can improve your gas mileage by 1-2 percent by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent. Also, look for motor oil that says "Energy Conserving" on the API performance symbol to be sure it contains friction-reducing additives.

10. Planning and combining trips Combining errands into one trip saves you time and money. Several short trips taken from a cold start can use twice as much fuel as a longer multipurpose trip covering the same distance when the engine is warm. Trip planning ensures that traveling is done when the engine is warmed-up and efficient.

With a little planning, you can avoid retracing your route and reduce the distance you travel as well. You'll not only save fuel, but also reduce wear and tear on your car.

11. Commuting

If you can stagger your work hours to avoid peak rush hours, you'll spend less time sitting in traffic and consume less fuel.

If you own more than one vehicle, drive the one that gets the best gas mileage whenever possible.

Consider telecommuting (working from home) if your employer permits.

Take advantage of carpools and ride-share programs. You can cut your weekly fuel costs in half and save wear on your car if you take turns driving with other commuters. In Central Oklahoma, access GetAroundOK.com, the Association of Central Oklahoma Government’s carpool matching program, helping citizens of central Oklahoma get to know each other better while saving gas, time and money!